Carburetor



Patented Mar. 2, 1943 CARBURETOR Victor B. Heftler, Grosse Pointe Park, Mich.

Original application July 30, 1940, Serial No. 348,431. Divided and this application January 7, 1941, Serial No. 373,460

Claims.

This application is a division of my co-pending application, Serial Number 348,431, filed July 30, 1940.

It is an object of this invention to provide a carburetor of the double Venturi type in which the main mixture conduit can be accurately machined before insertion of the secondary Venturi, and to provide means to permanently and securely fasten the secondary Venturi holder to the main carburetor casting after machining thereof.

Fig. 1 is a cross section of the pertinent part of a carburetor built according to this invention.

Fig. 2 is a partial cross section along the line 2-2 of Fig. 1.

Fig. 3 is a view showing the position of the secondary Venturi holder at a given stage of the assembling operation.

This invention is described as applied to a downdraft carburetor comprising a housing 2! leading downwardly to a throttle, not shown, and over which is secured a mixing chamber body member 22, which, in turn, supports a cover member 23, these three main parts being suitably fastened to one another by means not shown,

there being also a heat insulating gasket inserted between members 2| and 22.

Air enters through a conduit in the cover member 23 in register with conduit 26 in the mixing chamber body member, which conduit leads to conduit 2'! in the throttle housing 2!, and hence to the engine, not shown.

This main air passage affects the shape of a Venturi, and, to facilitate the adaptation of the carburetor to a given engine, I prefer to form a cylindrical bore '28 in the mixing chamber body member 22 and to insert therein a separate and removable Venturi suitably selected.

A secondary Venturi holder 30 is secured by its shank 3| to the mixing chamber body member 22, in which there is formed for this purpose a hole 32 having a squared bottom 33 and continued by a smaller hole 34!. Shank 3! is provided with a shoulder 35 and, close thereto, with a groove 36. Two holes 3'! and 38 are drilled in the casting constituting the mixing chamber body 'member 22 and open into the larger hole 32 so as to be substantially in registration with groove 3'6 when the shank of the Venturi holder in the mixing chamber body member 22 so that its shoulder 35 is in contact with seat 33. As shown in Fig. 2, hole 3? meets hole 32 squarely, while hole 3 3 its center line tangent thereto.

Fig. 5 shows how the shank of the secondary Venturi holder can easily be inserted in its place.

To hold it after insertion and in the position shown in Fig. l, a suitable alloy is melted into hole 33 and fills the groove 3'6 while air escapesthrough hole 3'! serving as a vent to avoid the formation of air holes in the cooled alloy. When the alloy has cooled, it forms a solid anchorage for the secondary Venturi holder, especially if the bottom of the groove is made non-circular, as for instance, by providing a small ridge 49 in the bottom thereof. The alloy is held against tendency to move by the intrusion of the metal into holes 3'! and 38, and the Venturi holder is prevented from turning by the ridge 69 actingas a key and from sliding along its axis by the meta1 in the groove. To make sure that the joint'will be tight against leakage of liquid fuel, I prefer to use an alloy that expands while cooling, such as the ternary eutectic of lead, tin and bismuth (32 per cent lead, 16 per cent tin and 52'per cent bismuth) which melts at 205 degrees Fahrenheit. As this temperature is much lower than the charring temperature for the phenolic resins, it is quite practical to use such material for the sec cndary Venturi holder, x

The secondary Venturi holder til is provided with two concentric bores 4i and 52, forming a shelf 43; the parts are so proportioned that, if the proper orientation of shank 3i is maintained during the solidification of the anchoring alloy and shoulder 35 in contact with the square-:1 bottom 33 of hole 32, the bores 41 and 42 will be substantially co-axial with the primary Venturi. 1

The secondary Venturi is preferably made in two pieces, the diverging delivery member 44 and.

\ the converging approach 45. The delivery mem her is located by its outside diameter into, the bore 42 and endwiseby a shoulder resting on the shelf 43. The approach member is locate-d by its outside diameter into the bore M. The inner surface of this member may be toroidaLas shown; so as to present 'good aerodynamic character istics. The outer and lower surface is in the form of a cone 49 so that the bottom of said member takes the form of a narrow ring 50.

By the assembly of these parts, an annular passage 5!, of triangular cross section, is formed between the bore 4|, the cone 49 of the approach member and a similar cone on the top of the delivery member. The outer diameter of ring 50 at the bottom ofthe approach member is made smaller than the inner diameter at the top of delivery member it, so that there is left, between these two pieces, a narrow circular slit 52, which would be continuous, were it not for the lugs 46. This slit affords communication bering 50 can be made very narrow, to allow the air flowing through the secondary Venturi to i draw fuel from the annulus with the minimum of eddies and the maximum atomization.

Should it be desiredto have the secondary venturi depart from a surface of revolution, so as to influence the distribution of fuel into the air stream, by the provision of vanes, for instance, the assembly of the parts into the secondary Venturi holder can be made with prefabricated parts in the proper angular position because of the fact that the assembly involve no rotation of the parts, as threaded parts would. i

Formed in the mixing chamber body member 22 is a constant level chamber for liquid fuel 54. Afuel supply line, not shown, may be connected to the threaded inlet 55, leading to the'needle valve 56, which is actuated, in the well known manner, by a level sensitive device, in this case a pair of floats symmetrically located with reference to the plane of Fig. 1, so that only one of them can be seen at 51. The parts are so made and proportioned that liquid fuel will fill chamber 54 to the level of line LL.

I have illustrated my invention as applied to a downdraft carburetor in which the fuel system embodies the well known system of compensation disclosed in the U. S. patent to Baverey, No. 907,953, as the provision of a separate Venturi holder just described present certain advantages which will be pointed out.

The shank of the secondary Venturi holder has, below the shoulder 35, an extension 58, smaller in diameter than hole 34, which it enters, so asto leave between the two a tubular passage 59. A well 60 is drilled into the mixing chamber body member, somewhat off i the plane of Fig. 1, but parallel thereto, and intersects hole 34 at 5 I; this well is open to the air pressure above the fuel in the constant level chamber 54, the latter being open to the air as is customary.

Screwed into the lower portion of hole 34 is a main jet tube 62, which projects into the hollow shank of the Venturi holder 3|, being spaced therefrom so as to form a second tubular passage 63 inside the shankof the Venturi holder. A

metering orifice 64 regulates the flow of fuel to.

shape passage of the Baverey patent, so well known in the art as embodied in the Zenith carburetor, can easily be traced: the air branch is made up of well 60 and tubular passage 59 which it intersects at 6|, the emulsion branch being tubular passage 63. By combining in one part the shank of the Venturi holder and the partition between the two branches of the U, a simple and inexpensive construction is obtained.

I claim:

j 1. In a. carburetor a body having a main air conduit, a lateral hole in said body, a liquid fuel supply nozzle structure having at one end a tubular shank to enter said hole and a fuel delivery member at the other end at an angle to said shank and a fastening body cast in situ in said 5 hole to secure and accurately position said nozzle structure in said body and to form a leakproof closure therebetween.

' 2. In a carburetor a body having a main air conduit, a lateral hole in said body opening into said air conduit, 2. liquid fuel supply nozzle structure having at one end a tubular shank to enter said hole, a step in said hole, a shoulder on said shank to co-act with said step to endwise locate said nozzle structure, a fuel delivery member at the other end of said nozzle structure and at an angle to said shank and a fastening body cast in situ in said hole to secure and accurately position said nozzle structure in said body and to form a leakproof closure therebetween.

3. In a carburetor, a body having a main air conduit provided with a lateral hole through its side wall, a liquid'fuel supply tube entering said hole and provided with an exterior annular recess, a pouring hole in said body to register with said recess, a fuel delivery member at the free end of said tube and at an angle thereto and a fastening body cast in said recess and in said pouring hole to endwise lock said tube into said body.

4. In a carburetor, the combination described in claim 3 in which the annular recess on the liquid fuel tube presents a departure from a surface of revolution co-axial with said tube so as to form with the cast'body an anchorage against rotation of said tube.

5. In a carburetor, a mixing chamber conduit having a curved surface, a hole extending through the curved wall of said conduit, a liquid fuel delivery tube having an end portion entering said hole and having at its other end a fuel delivery member secured and held in aligned position by said tube, and means to accurately position and rigidly hold said tube in said hole and to provide a gas and liquid tight seal comprising a body of lowmelting point alloy expanding upon freezing cast in situ and engaging said tube in said hole.

VICTOR R. HEFI'LER. 

